Device for recognizing a vehicle overturn

ABSTRACT

An apparatus for detecting a vehicle rollover includes a sensor suite for sensing vehicle dynamics data, the sensor suite being connected to a processor which is configured in such a way that the processor detects a vehicle rollover as a function of the vehicle dynamics data and the rollover sensor suite. The processor has means for dividing an operating state of the vehicle into chronologically successive phases. In particular, the processor has means for determining, for each phase, a float angle and a transverse vehicle velocity from the vehicle dynamics data; the float angle and the transverse vehicle velocity being used, together with the data from the rollover sensor suite, for detection of the vehicle rollover.

FIELD OF THE INVENTION

The invention proceeds from an apparatus for detecting a vehiclerollover.

BACKGROUND INFORMATION

German patent document DE 199 10 596 describes triggering restraintmeans as a function of vehicle dynamics data. Such data from, e.g., anESP system can be used.

German Patent document DE 101 49 112 discloses a method for determininga triggering decision for restraint means in a vehicle, which methodmakes a triggering decision as a function of a float angle, a transversevehicle velocity, and the vehicle tilt angle. The maximally achievablevehicle tilt angle is characterized by way of a transverse vehicleacceleration and/or a transverse vehicle velocity. An occupant detectionsystem can additionally be used.

SUMMARY

The apparatus according to the present invention for detecting a vehiclerollover has the advantage that because the vehicle state is subdividedinto chronologically successive phases, a corresponding determination ofthe float angle for the individual phases is possible. In other words, aseparate calculation protocol for the float angle is used for eachphase. This then makes possible, in particular, a determination of thefloat angle in the angle range greater than 10 degrees. The lateralvelocity is also determined in this context. For vehicle rollovers withhigh lateral acceleration it is thus possible, in interaction with therollover sensor suite (rotation rate about the longitudinal axis ω_(x),transverse vehicle acceleration a_(y), and optionally vertical vehicleacceleration a_(z)), to arrive at a reliable triggering decision at verysmall roll angles, thus allowing considerably improved occupantprotection as compared with conventional systems. The reason for this isthat the lateral velocity, and therefore implicitly the float angle,decisively influences the rollover in the event of a soil trip. Thefloat angle and the lateral velocity may be determined by multi-stagelogic. A variety of calculation methods are combined for this purpose,and an implementation of the selection of the respective method isdescribed. The method may be characterized by a sensing of thelongitudinal velocity, the yaw rate (i.e. the rotation rate about thevertical axis of the vehicle), the lateral acceleration, and optionallythe wheel rotation speeds, the longitudinal acceleration, and thesteering angle, and an estimate of the float angle.

The operating state of a vehicle can be divided, for purposes of thepresent invention, into three categories that a vehicle passes throughsuccessively in the context of a skid. These are thereforechronologically successive phases. A change from an advanced phase backinto a previous state can, however, also occur. These are, e.g., thestable operating state, a skidding motion (which can also be referred toas the breakaway state), and the skid or skid state itself.

It is advantageous that the stable operating state is characterized by asmall and (for purposes of rollover detection) almost constant floatangle, the skidding motion by a large change in float angle, and theskid by a float angle that exceeds a predefined threshold value. Thisallows the phases to be identified in order to select the correspondingcalculation protocol for the float angle.

As discussed above, it is possible for the sensor suite not only todetermine measured and estimated or calculated vehicle dynamics datasuch as longitudinal vehicle velocity, yaw rate, and a transversevehicle acceleration, but also to evaluate further calculated ormeasured variables such as wheel rotation speeds, acceleration in thelongitudinal vehicle direction, steering angle, and a float angle thathas been ascertained, for example, by way of a control unit for thevehicle dynamics control system. In present-day systems for vehicledynamics control, however, the latter value has validity only for smallfloat angles, since the vehicle state can be successfully influencedonly for float angles of a few degrees, and only that range musttherefore be acted upon. A device for measuring the float angle and/orthe transverse vehicle velocity can also be used.

Lastly, it is also advantageous that the apparatus according to thepresent invention is connectable to a restraint system that activatesthe processor of the apparatus as a function of detection of a rollover.The result, in particular, is that according to the present inventionthe triggering of such restraint means, by utilization of the floatangle β and lateral vehicle acceleration velocity V_(y) in addition tothe rollover sensor suite (ω_(x), a_(y) and a_(z)), becomes moreaccurate and more situationally appropriate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the apparatus according to the presentinvention.

FIG. 2 is a flow chart of the sequence executed by the apparatusaccording to the present invention.

FIG. 3 is a state diagram for the sequence of the apparatus according tothe present invention.

FIG. 4 is a block diagram indicating the parameters characteristic ofthe stable operating state.

FIG. 5 is a second block diagram characterizing the stable operatingstate.

FIG. 6 is a first block diagram characterizing the breakaway state.

FIG. 7 is a second block diagram characterizing the breakaway state.

FIG. 8 is a first block diagram characterizing the skid state.

FIG. 9 is a second block diagram characterizing the skid state.

DETAILED DESCRIPTION

Modern vehicles are equipped with restraint means, for example a windowairbag or belt tensioner, that allows the occupants to be protected inthe event of a vehicle rollover. Existing systems for rollover detectionconsider the roll motion and the accelerations in the X, Y, and Zdirections of the vehicle. Reliable detection of a vehicle rollover ispossible on this basis. The decision cannot be made, however, until alate point in time during the rollover, typically at a roll angle of 20to 40 degrees. In certain instances of vehicle rollovers, however,(so-called “soil trips”), this is too late for sufficient protection ofthe occupant, since as a result of the high lateral acceleration he hasalready experienced a sideways displacement that greatly limits theusefulness of, for example, window airbags. As indicated in the existingart, a method is already known that makes possible a timely triggeringdecision in a context of high lateral acceleration by also incorporatingthe float angle and the lateral acceleration of the vehicle.

The present invention provides, for determining the float angle in theangular range greater than 20 degrees and the lateral velocity that areto be used for rollover detection, an apparatus that subdivides theoperating state of a vehicle into chronologically successive phases, adetermination of the float angle and of the transverse vehicle velocityfrom the vehicle dynamics data being performed for each phase, and thetype of determination of the float angle and of the transverse vehiclevelocity being different in the individual phases.

The determination method, e.g., a calculation method, is preciselyallocated to the respective phase and takes into account the physicalcircumstances of that phase. Three phases, for example, aredistinguished: the stable vehicle state; a skidding motion that is alsoreferred to as the breakaway state; and the skid itself, i.e., the skidstate.

The float angle and the lateral velocity V_(y) are to be determinedhereinafter by multi-stage logic. A variety of calculation methods arecombined for that purpose, and an implementation of the selection of therespective method is described.

FIG. 1 is a block diagram of the apparatus according to the presentinvention. A sensor suite 1 is connected via a data output to aprocessor 2. Processor 2, which also has memory means, is connected viaa data output to a restraint system 3. Sensor suite 1 supplies vehicledynamics data and rollover data (yaw rate and horizontal accelerations).Sensor suite 1 has acceleration and rotation-rate sensors for thatpurpose. Sensing of the wheel rotation speed and the steering angle canalso be provided in sensor suite 1. Sensor suite 1 can be distributed inthe vehicle and/or concentrated in a central control device. Here sensorsuite 1 supplies a digital signal to processor 2. Digital sensors thatalready output a digitized sensor signal are generally used.

It is possible to use analog sensors whose signal is digitized either inprocessor 2 or by way of a separate analog/digital converter.Digitization is necessary for further processing. Sensor suite 1 canalso encompass a control unit for vehicle dynamics control that canindicate an estimated value for a float angle at small angles. Suchvehicle dynamics control systems are generally suitable only for angleranges below 10 degrees, for example, methods that use a model made upof tire characteristics and lateral guidance force. Vehicle dynamicscontrol may no longer be performed successfully, in particular, atgreater float angles. Sensor suite 1 can likewise have a control unitthat supplies calculated or prepared variables, for example, thelongitudinal vehicle velocity.

Sensor suite 1 can therefore, as indicated above, be disposed outside ahousing in which processor 2 is located. The electrical connectionbetween sensor suite 1 and processor 2 can be implemented by way of abus or a two-wire conductor or a plurality of two-wire conductors. Inthe case of two-wire conductors, it is possible for the information flowto be established unidirectionally from sensor suite 1 to processor 2.

In addition to the conventional rollover sensor suite (ω_(x), a_(y), anda_(z)), processor 2 evaluates the vehicle dynamics data of sensor suite1 and can detect a vehicle rollover therefrom by ascertaining the floatangle and the transverse vehicle velocity. The float angle and thetransverse vehicle acceleration are now determined here as a function ofthe identified phase of the operating state. A separate calculationprotocol is provided for each phase. Here, three phases may be provided:the stable operating state, a breakaway state, and the skid state. Asubdivision into more or fewer than three phases is also possible.

The vehicle is initially in the stable operating state, which includescornering at a low float angle. When this state exists, the float angleand the lateral velocity are of no interest for rollover detectionbecause they are too low to initiate a rollover motion. The valueresulting as an estimated lateral velocity v_(y0) is therefore zero. Inthis phase, the estimated float angle β₀ can be regarded as a constantfor rollover detection, the constant being vehicle-dependent and beingdetermined by way of the maximum achievable float angle duringcornering. As an alternative, it is also possible to use the float angleβ_(ESP), as calculated, e.g., in a control unit using tirecharacteristic models, as a transfer value for the next state. A furtheralternative is to determine the float angle β₀ that is to be used at thetransition to phase 2 by estimating the vehicle situation, for exampleon the basis of a steering angle (suitably filtered, if applicable), theyaw rate, and the transverse vehicle acceleration.

The second phase is characterized by an incipient skidding motion. Thiscan be detected, for example, by way of a large change in float angle ora sharp drop in a lateral acceleration previously of longer duration.The basis for this is that a skid begins, inter alia, when the lateralguidance forces during cornering are no longer sufficient to keep thevehicle stable, and the wheels therefore slip laterally.

The change in float angle is calculated using the following equation:

$\begin{matrix}{\overset{.}{\beta} = {\omega_{z}\frac{{a_{y}{\cos^{2}(\beta)}} + {a_{x}{\cos(\beta)}{\sin(\beta)}}}{v_{x}}}} \\{\approx {\omega_{z} - {\frac{a_{y}}{v_{x}}\mspace{14mu}{for}\mspace{14mu}{small}\mspace{14mu}{values}\mspace{14mu}{of}\mspace{14mu}\beta}}}\end{matrix}$

In this phase the float angle β₁ can be determined by additivelyintegrating the change in float angle, taking as the initial value thepreviously ascertained value β₀ from phase 1. This is then determinedwith the following equation:β₁=β₀ +∫{dot over (β)}dt

The lateral velocity V_(y) is then obtained from the float angle β₁ andthe vehicle's longitudinal velocity v_(x):v _(y,1) =v _(x) tan(β₁).

The third phase is characterized by skidding of the vehicle. This isdetectable, for example, by way of a float angle β₁ beyond a specificthreshold β_(min) and/or by locking of the wheels at a yaw rate ω_(z)greater than a minimum yaw rate ω_(zmin).

The float angle β₂ is then calculated by additive integration of the yawrate, the previously ascertained value β₁ from the second phase beingtaken as the initial value;β₂=β₁+∫ω₂ dt.

The lateral velocity is then obtained from the float angle and thecenter-of-mass velocity V_(sp) of the vehicle:v _(y,2) =v _(sp) sin(β₂).

The center-of-mass velocity is obtained from the initial longitudinalvelocity, the initial lateral velocity, and the lateral accelerationa_(y), and optionally the longitudinal acceleration a_(x).

FIG. 2 is a flow chart illustrating the sequence occurring in theapparatus according to the present invention shown in FIG. 1. In methodstep 4, sensor suite 1 delivers the vehicle dynamics data to processor2. Method step 5 then checks whether the stable state is being departedfrom, i.e. whether a breakaway situation exists. Processor 2 checks thison the basis of the vehicle dynamics data. If that is not the case,execution branches back to method step 4. If it is the case, however,the breakaway state is then detected in method step 6 and the floatangle is determined as described above. This also applies to thetransverse vehicle velocity. Method step 7 then checks whether phase 3,i.e., the skid state, has been reached. If that is not the case,execution branches back to method step 5. If it is the case, however,execution then branches to method step 8 and we are in the detected skidstate, the float angle and transverse vehicle velocity now beingdetermined as indicated above. Method step 9 then checks whether avehicle rollover has been detected on the basis of the vehicle dynamicsdata and the rollover sensor suite (ω_(x), a_(y), and a_(z)). If that isnot the case, execution branches back to method step 5. If it is thecase, however, execution then branches to method step 10, and restraintmeans 3 are activated by processor 2. In the context of a vehiclerollover, these are, for example, airbags that protect the head regionin particular, a roll bar, and belt tensioners that prevent the personfrom sliding out (i.e., the “submarining” effect) during a rollover.

FIG. 3 shows a diagram of the states through which the apparatusaccording to the present invention passes. From a stable operating state11, the apparatus moves into breakaway state 12 when, as presentedabove, a breakaway detection exists. The transfer parameter that istransferred is the float angle β₀. In breakaway state 12, a check ismade as to whether a stable state is detected or a skid state exists. Ifa stable operating state was detected, the system then moves frombreakaway state 12 back into stable operating state 11. If a skid stateis detected, however, the system then moves to state 13 (the skidstate), and the float angle β₁ is transferred as a parameter.

If neither of the two is present, the system remains in breakaway state12. In the skid state, a check is then made as to whether the stableoperating state again exists. In that case the system moves from state13 back into stable operating state 11. A check is also made as towhether the restraint means are to be triggered.

FIG. 4 shows that the estimated float angle value β₀ and a transversevehicle velocity of zero are present as output parameters of the stableoperating state. FIG. 5 depicts a variant in which the float angleβ_(ESP) is supplied by the vehicle dynamics control system. In that caseas well, the float angle β₀ and a transverse vehicle velocity V_(y)equal to zero are present as output values.

FIG. 6 shows the parameters involved in determining the float angle β₁and transverse vehicle velocity v_(y1) in the breakaway state. Thisrequires the float angle β₀ from the stable operating state, thelongitudinal vehicle velocity v_(x), the yaw rate ω_(z), the transversevehicle acceleration a_(y), and the longitudinal vehicle accelerationa_(x). As shown in FIG. 7, it is also possible to omit the longitudinalvehicle acceleration and to determine the float angle β₁ and transversevehicle velocity v_(y1) using only the float angle β₀, longitudinalvehicle velocity v_(x), yaw rate ω_(z), and transverse vehicleacceleration a_(y).

FIG. 8 shows the parameters necessary for determination of the floatangle β₂ and transverse vehicle velocity v_(y2) in the skid state. Herethese are the float angle β₁, longitudinal vehicle velocity v_(x), yawrate ω_(z), transverse vehicle velocity v_(y1), longitudinal vehicleacceleration a_(x), and transverse vehicle acceleration a_(y). Asdepicted in FIG. 9, it is alternatively possible to omit thelongitudinal vehicle acceleration.

1. An apparatus for detecting a vehicle rollover, comprising: a sensorarrangement for sensing vehicle dynamics data and rollover data; and aprocessor connected to the sensor arrangement, wherein the processorcategorizes an operating state of the vehicle into one of a plurality ofsuccessive phases, and wherein the processor determines, for each phase,a float angle and a transverse vehicle velocity from the vehicledynamics data and the rollover data, and wherein the vehicle rollover isdetected based on the float angle and the transverse vehicle velocitywherein chronologically successive phases include a stable operatingstate, a breakaway state, and a skid state, wherein the stable operatingstate is characterized by a constant value of the float angle, thebreakaway state is characterized by an increase in the float angle by atleast 20 degrees, and the skid state is characterized as occurring afterthe breakaway state has occurred and where the vehicle is skidding andof the float.
 2. The apparatus as recited in claim 1, wherein thevehicle dynamics data includes at least one of a longitudinal vehiclevelocity, a yaw rate and a transverse vehicle acceleration.
 3. Theapparatus as recited in claim 1, wherein the vehicle dynamics dataincludes at least one of a longitudinal vehicle velocity, a yaw rate anda transverse vehicle acceleration.
 4. The apparatus as recited in claim2, wherein the sensor arrangement additionally detects and outputs atleast one of a wheel rotational speed, a longitudinal vehicleacceleration, a steering angle, and an estimate of the float angle. 5.The apparatus as recited in claim 3, wherein the sensor arrangementadditionally detects and outputs at least one of a wheel rotationalspeed, a longitudinal vehicle acceleration, a steering angle, and anestimate of the float angle.
 6. The apparatus as recited in claim 1,wherein the apparatus is connected to a restraint system that isactivated by the processor based on the detection of the rollover. 7.The apparatus as recited in claim 1, wherein the apparatus is connectedto a restraint system that is activated by the processor based on thedetection of the rollover.
 8. The apparatus as recited in claim 2,wherein the apparatus is connected to a restraint system that isactivated by the processor based on the detection of the rollover. 9.The apparatus as recited in claim 3, wherein the apparatus is connectedto a restraint system that is activated by the processor based on thedetection of the rollover.
 10. The apparatus as recited in claim 4,wherein the apparatus is connected to a restraint system that isactivated by the processor based on the detection of the rollover. 11.The apparatus as recited in claim 5, wherein the apparatus is connectedto a restraint system that is activated by the processor based on thedetection of the rollover.